The invention concerns spinal osteosynthesis systems, in particular for anterior fixation.
Spinal osteosynthesis systems for anterior fixation are known in which the connection elements are formed by plates, and others are known in which the connection elements are formed by rods. Because of their bulk, the systems based on plates are difficult to use, if they can be used at all, via the endoscopic route. Moreover, their limited size (length) means that they can only be used for simple vertebrectomies involving a single vertebra, or perhaps two. It is impossible to treat scoliosis with this type of implant. Finally, the plates are difficult to adapt to the morphology of the vertebra in which they are anchored. Moreover, the systems based on rods generally comprise fairly voluminous connectors which cannot always be used via the endoscopic route.
A spinal osteosynthesis device is also known from document FR-2,731,344, the counterpart of WO-96/27340, which device comprises a connector with two branches which can clamp a connection rod between them, the branches being able to be engaged on a vertebral pedicle screw. However, this connector, while well suited for posterior fixation of the spine on the vertebral pedicles, does not ensure sufficient stability with a view to anterior fixation of the spine.
An object of the invention is to make available a spinal osteosynthesis system of a different type, adapted for anterior fixation, easy to fit, ensuring good stability of the system on the spine, and compatible with being fitted via the endoscopic route.
To achieve this object, the invention provides a spinal osteosynthesis system comprising an elongate connection element, a vertebral screw, and a connector including two branches which are able to clamp the connection element between them, at least a first of the branches being able to be engaged on the screw, the system comprising a second vertebral screw, the first branch having an extension which can be engaged on the second screw.
Thus, the connector can be rendered less voluminous so that it can be put into place via the normal or endoscopic route. Moreover, the fixation of the connector to the vertebra by means of the two screws permits precise, stable and reliable positioning of the connector and thus of the connection element. This connector is easy to join to the connection element and to the screws. These advantages make this connector particularly well suited to anterior fixation of the spine. The connector will preferably be in one piece.
Advantageously, the extension has an opening for receiving the second screw.
Advantageously, the extension has a spherical recess at one edge of the opening intended to be remote from the vertebra.
Thus, it is possible to control the angle of the second screw relative to the connector in order to better adapt the system to the configuration of the vertebra.
Advantageously, one of the branches which is intended to be remote from the vertebra has an opening for receiving the first screw, and a spherical recess at one edge of the opening intended to be remote from the vertebra.
Thus, it is possible to control the angle of the first screw relative to the connector in order to better adapt the system to the configuration of the vertebra.
Advantageously, the extended branch can be bent manually, in particular using a tool.
Thus, it is possible to adapt the shape of the connector to that of the vertebra and in particular to position the connector very close to the latter.
Advantageously, the first screw includes a head and a flange distinct from the head and able to cooperate with one of the branches which is intended to be adjacent to the vertebra, in order to immobilize the connector in terms of rotation relative to the first screw.
Thus, upon fitting, prior immobilization of the connector relative to the first screw is obtained, facilitating the positioning of the other elements and making it possible to effect positional corrections, all this before final clamping of the fitted system.
Advantageously, the flange has a face, which is in particular a conical face, able to immobilize the connector by friction.
Advantageously, the first screw has a threaded orifice, the system comprising a clamping screw which can constitute a screw-nut connection with this orifice and is able to bear on one of the branches which is intended to be remote from the vertebra in order to clamp the branches.
Thus, it is possible first to fit the first screw, the connector and the second screw, and only later to install the clamping screw in order to proceed with clamping of the assembly.
Advantageously, the system comprises a ring which can be engaged on the rod and received between the branches, the connector and the ring being designed to permit control of the orientation of the rod in two mutually perpendicular planes before the branches are clamped.
Advantageously, the two branches form part of a single component which is elastically deformable in order for the branches to be closed towards each other.
Advantageously, the connector can be fixed to the vertebral screw and to the first connection element by choosing an angular position of the connection element relative to the connector.
It has also been noted that the device in document FR-2,731,344 mentioned above does not always afford sufficient rigidity for anterior fixation of the spine.
Consequently, a subsidiary object of the invention is to provide a system suited for anterior fixation and ensuring a particularly high degree of rigidity.
To achieve this object, the system advantageously comprises a second elongate connection element, the connector being able to be fixed simultaneously to the two connection elements.
Thus, the presence of the two connection elements gives the system very great rigidity, without complicating its assembly, without increasing the volume of its various components (which renders it compatible with fitting via the endoscopic route), and while maintaining the possibility of controlling the angular position of the connector relative to the first connection element. The system according to the invention does not require identical bending on the two connection elements. Moreover, the number of connectors can remain small.
Advantageously, the system is designed in such a way that the second connection element can be fixed to the connector only in a single angular position relative to the connector.
Thus, the shape of the second connection element dictates the relative angular position of the connectors which are fixed to it. This angular position can therefore be chosen in advance depending on the prior curvature given to this connection element, either at the time of manufacture or, better still, during the surgical intervention.
Advantageously, the second connection element has less resistance to bending than the first connection element.
Thus, the first connection element has mainly a function ensuring support of the connectors, and the second connection element has mainly a function ensuring relative angular positioning of the connectors.
Advantageously, the branches can simultaneously clamp the two connection elements.
Advantageously, the system is designed in such a way that the second connection element, when fixed to the connector, extends in a trajectory of the second vertebral screw for its disengagement from the connector.
Thus, the second screw is prevented from starting to come out at an inopportune moment.
Advantageously, the system comprises a second connector, the two connectors each being able to be fixed simultaneously to the two connection elements.
Advantageously, the system is intended to be fixed on the anterior part of the spine.
The invention also provides a connector for a spinal osteosynthesis system, including two branches which can clamp an elongate connection element between them, at least a first of the branches having an opening which can be engaged on a vertebral screw, and in which the first branch has an extension having an opening which can be engaged on a second vertebral screw.
This connector is adapted to form part of the system according to the invention.